Tire treads are required to have high properties such as mainly fuel economy, abrasion resistance, and wet grip performance. Various techniques for improving these properties have been studied.
For example, fuel economy is known to be improved by introducing a functional group having an affinity for filler into a polymer chain end. Abrasion resistance is known to be improved by using a high molecular weight polymer having a molecular weight of 250,000 or more. Wet grip performance is known to be improved by using a polymer having a high glass transition temperature (Tg).
However, the introduction of a functional group having an affinity for filler, the use of a high molecular weight polymer, and the use of a polymer having a high Tg resulting from increased styrene content all unfortunately increase the hardness of rubber compositions, thereby deteriorating processability.
Patent Literature 1 discloses a tire rubber composition containing a liquid resin having a softening point of −20° C. to 45° C. and a specific silica to improve fuel economy, abrasion resistance, and wet grip performance. However, there is still room for improvement to achieve a balanced improvement in these properties while ensuring good processability.